Superhydrophobic and superoleophilic membranes for oil-water separation application: A comprehensive review

Superhydrophobic and superoleophilic (SHSO) membranes have gained remarkable attention, particularly in selective and efficient oil-water separation applications. This paper provides a comprehensive review of the SHSO membranes, fabrication and characterization methods, the advantages and disadvantages of the fabrication techniques, current status and prospects of SHSO surfaces, and potential future research directions. Chemicals such as silanes, thiols, fatty acids, carbon nanotubes, and polyethylene-based polymers are commonly used to adjust the surface energy for the SHSO membranes. These membranes have been proven successful in selectively separating oil from oil-water mixtures with oil separation efficiency >99%. Although there are limited studies on the short-term stability assessment of the SHSO coatings upon exposure to acid and alkaline environments, the effects of temperature, and adsorption of heavier components of the crude oils (such as asphaltenes, and resins) on the separation efficiency have not been adequately investigated yet. Moreover, the fouling performance of the SHSO membranes with water-derived fouling is surprisingly missing in oil-water separation applications in the literature. With the breakthrough in technology, the use of 2D materials such as graphene and high-resolution 3D printers to create hierarchical features on membranes, research on application of SHSO membranes in oil-water separation processes can be further advanced.